Piano capacitor reactor



March 7, 1961 c. c. NOLDER HAL 2,973,680

PIANO CAPACITOR REACTOR Filed Aug. 8, 1955 2 Sheets-Sheell 1 INVENTOR: CL/FF C. News@ BY is Pfl/MP5 .ERE NN L NN mw Mafch 7, 1961 C, C, NOLDER ETAL 2,973,680

PIANO CAPACITOR REACTOR 2 Sheets-Sheet 2 Filed Aug. 8, 1955 INVENToRs Cuff: c, Mamie 55 c//LL/.;

9' far/ze n yvvvvvvv United States Patent" PIANO cArAcrroR REACToR Charles Clifford Nolder, Corona Del Marrand Leslie Phillips, Santa Ana, Calif., assignors to Electronic Pianos, Inc., Santa Ana, Calif.

Fried Aug. s, 195s, ser. No. 527,062

s claims. (c1. s4-i.14)

The invention relates to sound reproduction systems,

and in particular an electronic capacitor pick-up and amplifying system applicable to string instruments in general and particularly well adapted to a piano.

. Improvements in electronic amplification systems have given rise to a variety of adaptations of such systems to musical instruments. For the most part systems of this type are, in effect, a microphone adjacent the source of sound and an attendant system so `designed as to be capable of discarding some of the undesired frequencies and reproducing the musical tones by use of an amplification system similar to those commonly employed in radio loudspeakers.

Other phases of this art have been directed to musical instruments such as electric organs, where musical notes are generated by some particular system somewhat foreign to conventional organ tubes, and the musical sounds thus created modified and altered in an assortment of ways to produce unique vsonic .effects as those effects may be desired by the artist who has available a series of stops enabling the instrument to be shifted from one character of sound to another.

Although these musical `reproduction systems have had an appeal of a certain type, in the main t-hey have lacked certain characteristics normally expected by music lovers to the extent that they produce a somewhat unnatural sound.

It is therefore among the objects of the invention to provide a new and improved electrical pick-up and amplification system which is capable of producing musical sounds from a stringed instrument' of such character that they have a very true and pleasing effect upon the listener.

Another object of the invention is to provide a new and improved electronic pick-up and amplication systern for astringedinstrument which reproduces in the form of sound waves the vibrations of the strings without the necessity ofthe strings themselves generating an initial sound with or without :the aid of a sounding board.

Another object of the invention is to provide a new and improved electronic pick-upand amplication systern for a string instrument,v and in particular a piano, which is able to greatly iirlpr'ove' .thel musical quality of an instrument such as a piano," the system furthermore being capable of variations such as may be produced by `damping out certain strings so that'the sound is produced by the vibrations on only one string at each tone interval or on occasions ori two strings at each tone interval instead of three strings as is the case throughout a large portion of the tone range of a piano.

A still further object of the invention is to provide a new and improved electronicpick-up and amplication system for an instrument such as a piano which is of simple construction and design and which moreover is of such character that it can be either applied to virtually any commercial piano of present manufacture or built into theinstrument at the time that it is manufactured.

With these and Lother objects in view, the invention consists in the construction, arrangement, and combination of the various parts of the device, whereby the objects contemplated are attained, as hereinafter set forth, pointed out in the appended claims, and illustrated in the accompanying drawings.

In the drawings:

Figure l is a plan view of a piano frame somewhat conventionalized illustrating base, middle range, and upper range sets of strings and the relative location of the pick-up mechanism of the invention.

Figure 2 is an enlarged plan view of one form of the pick-up mechanism.

Figure 3 is a fragmentary sectional view illustrating the means by which the pick-up mechanism is attached to a piano frame.

Figure 4 is a cross-sectional view taken on the line 4 4 of Figure 1 showing one form of the invention.

Figure 5 is a cross-sectional view showing a modified form of the invention.

Figure 6 is a cross-sectional view showing still another modified form ofthe invention.

Figure'7 is a partially broken away perspective view of the pick-up elements of the electrical system.

Figure 8 is a wiring diagram of the electrical portion of the system.

Figure 9 is a fragmentary view of the treble portion of a piano illustrating a damping mechanism for selectively damping out certain strings.

Figure 10 is an enlarged fragmentary side elevational view of one end of the damping mechanism.

Figure 1l is a cross-sectional View taken on the line 11-11 of Figure 10 showing one string of a trio of strings in damped out condition.

Figure 12 is a cross-sectional view similar to Figure ll showing the position of the damping mechanism when two strings out of a trio of strings are damped out.

Figure 13 is an end elevational View of the damping mechanism of Figure l0.

In an embodiment chosen for the purpose of illustration there is shown what may be considered as a' conventional piano housed in a casing 10 in which is mounted a frame 11. Normally a sound board 12 will be provided adjacent the strings in order to amplify and direct the tones normally generated by vibrating strings when they are struck by the hammers iny the usual fashion. As pianos are normally built, the strings are divided into three sets7 namely, a base set 13, a treble set 14, and an upper set which is an octave above the treble set. Ordinarily the lower ten or twelve base strings are single strings and the remaining strings in the base set are two strings for each tone interval.

tor pick-up 18 overlies t-he strings of the range above the treble set. While the capacitor pick-up is not of a highly critical character, nevertheless the metallic portion of it must be comparable to a degree to the weight and mass of the strings over which it is placed. The capacitor pick-up 16 is shown in section in Figure 4. The capacitor pick-ups 17 and 18 are similar in all general respects suicient that a description of one will suice for all three.

In the embodiment of Figure 4, the capacitor consists of a lower sheet 19 of dielectric damping material laminated with an upper sheet 20 of the same material, between which are located a series of three metallic bands or wires 21, 22 and 23. These wires are embedded in Patented Mar. 7, 1961 the sheets of dielectric damping material which in turn are cemented together, the embedding of the wires being such that the wires are permitted no vibration or movement. A satisfactory damping material comprises a fiber-laminated thermosetting plastic of a tough somewhat rigid consistency.

Above lthe sheet 20 is a second set of bands or wires 24, 25 and 26, these last identified bands or wires being located respectively in parallel alignment with the tirst identified wires and securely fastened to the upper face of the sheet 20 so that these last identified wires also are permitted no vibratory or other movement.

As illustrated in Figure 7, the wires 21, 22 andV 23 are electrically connected by a cross lead 27. The wires 24, 25 and 26 are connected together by a cross lead 28 and the leads in turn are electrically connected to a wire 29.

In position on the instrument, such as a piano, the capacitor pick-up 16 in the illustration described is securely fastened to the piano frame and occupies a position spaced from the strings 3Q, as illustrated in Figure 4. It has been found in practice that good results Can be secured when a capacitor or capacitor element f the type herein described is spaced about 1A inch from the strings and wherein the capacitor element itself has an over-all thickness of about 1A inch equally divided between two sheets 1A@ inch in thickness. The spacing of the capacitor from the strings is again critical and will be productive of good results when varied between distances of 1/6 and 1A inch.

As will be noted from examination of Figure 1, the capacitor pick-up strip, indicated generally by the reference character 16, spans all of the string of the base section 13. In order to properly fasten the capacitor pickup in place in spaced relationship to the strings, a fastening means must be employed which will so fix the location of the capacitor pickup that it does not shift in position either longitudinally, laterally or toward or away from the strings. It must be rigidly maintained in its selected position at all times, except for the provision of a means for adjusting it in the first instance.

A form of securing device found acceptable is shown in Figure 3, wherein a bushing 35 of some appropriate Vibration absorbing non-conductor is mounted in a suitable aperture 36 in the frame 11. A material such as fiber laminated rubber or plastic of suitable non-brittle consistency will be found acceptable. The bushing may be cemented or otherwise held in place in the aperture in the frame. A spring 37 yieldable but relatively stiff serves as a spacer between the capacitor pickup and the frame. To hold the capacitor pickup in position, there is provided a bolt or cap screw 38 which extends through an appropriate aperture in the capacitor pickup and preferably extends by employment of self-cutting threads 39 into the bushing 35. It is found advisable to employ three such mountings, indicated generally by the reference characters 39, 40, and 41, in staggered relationship so that the capacitor pickup is secured against rocking movement as well as against any other movement. By selecting a spring 37 of suitable length and resistance, the spring will hold the capacitor pickup outwardly but can be made to compress when the cap screw 38 is adjusted to permit the capacitor pickup to be drawn closer to the strings. It is important further that there be no electric connection between the capacitor pickup and the frame and further that the connection be dampened so that there is no transmission of Vibration therebetween.

In the arrangement shown, the capacitor pickups 16, 17, and 18 are shown connected in series. It should be appreciated, however, that it is not important that a series connection be used in that a parallel arrangement is equally satisfactory.

As indicated, the capacitor pickup 16 is connected by means of wire 29 to the capacitor pickup 17, which in turn is connected by means of wire 40 to the capacitor pickup 18. A shielded wire cable 41 may be employed to connect the capacitor pickups to a modulated oscillat-or 43, as shown in Figure l. By using a shielded cable, the shield can be grounded and a positive connection made between the capacitor bands or wires and the circuit of the modulated oscillator. As shown in Figure 8, the strings 30 are connected by means of a lead 42 to ground. Ground therefore supplies one of the connections for the capacitor circuit, having in mind that a capacitor effect is set up between the stationary capacitor pickup on one hand and the strings on the other hand which move in response to being struck and vibrate at a predetermined frequency and amplitude to vary reactance between the string and the capacitor pickup, thereby to vary the capacitance of the circuit just described.

In the diagram illustrated in Figure 8, that portion ot the circuit comprehended between the broken lines and marked with the reference character 43 may be described as a capacity modulated oscillator. The next portion to the right comprehended between the broken lines and marked with the reference character 44 may be described as a detector. The portion of the circuit on the right and between the broken lines indicated by the reference character 45 may be considered as a preamplifier. From the pre-amplifier, a lead 46 may connect with a conventional loudspeaker amplification circuit.

The modulated oscillator indicated by the reference character 43 in the embodiment chosen for the purpose of illustration incorporates an oscillator element or tube 47, which, in cooperation with the other portions of the circuit indicated and appropriately labelled, may cooperate with the tube 48, if such tube be employed, to set up a carrier frequency for transmitting the capacitor effect produced by the vibrating strings of the instrument. In the embodiment selected for the purpose of illustration values for the various portions of thecircuit which are productive of a successful working embodiment are as follows:

C1 100 mmfd., 600 v. C2 100 mmfd., 600 v. C3 .0l mfd., 400 V.

C4 5 mmfd., 600 v.

C5 1000 mmfd., 600 v. C6 '100 mmfd., 600 v. C7 270 mmfd., 600 v. C8 .o1 mfd., 400 v.

C9 .01 mfd., 400 v.

C10 .01 mfd., 400 v. C11 '20 mfd., 375 v. C12 40 mfd., 37S v. C13 80 mfd., 375 v. C14 100 mfd., 150 v. C15 .01 mfd., 400 v.

R1 39K, 1/2 watt.

R2 22K, 1/2 watt.

R3 56K, 1/2 watt.

R4 270K, 1/2 watt.

R5 1K, 1/2 watt.

R6 220K, 1/2 watt.

R7 220K, 1/2 watt.

R8 120K, 1/2 watt.

R9 68K, 1/2 watt.

R10 1 meg. vol. control. R11 220K, 1/2 watt. R12 1K, 1/2 watt.

R13 3900 v., 2 watt. R14 3900 v., 2 watt. R15 50 v., 1 watt.

R16 l 27K, 1/2 watt. V T1 Miller B-32'1-M. 'j T2 Miller 6205:

T3 Y Stane orPCl34. Sel 65 mil.

V3 6AV6.

In another form of the capacitor pickup, illustrated in Figure 5, the metallic elements of the pickup may assume a slightly different form. As there shown, the capacitor pickup consists, as previously indicated, of lower and upper sheets 50 and 51, respectively, of dielectric damping material laminated and enclosing between them a sheet or strip of imperforate thin sheet metal 52. The material of the sheet metal strip 52, as in the case of the wires 21 through 26, previously described, is preferably copper or brass. In practice, it has been found that a sheet about two inches wide and about .005 inch thick produces satisfactory results. Overlying the sheet 51 are three bars or wires 53, 54, and 55. Although not expressly shown, it will be appreciated that all of the wires 53, 54, and 55 are connected together at their ends and connected also to the sheet 52 of imperforate strip metal. The capacitor pickup' of Figure 5 is otherwise used in the same fashion as has already been described in connection with I the capacitor pickup 16.

In still a third modified form of the device, a capacitor pickup is illustrated in Figure 6 as comprising lower and upper sheets 65 and 66, respectively, of a dielectric dampening material laminated together and holding between them a strip 67 of brass' or copper of the same thickness as was described in connection with Figure 5 or perhaps slightly thicker in order to provide a sufficient area of metal in the capacitor to balance the metal in the adjacent strings 30. l,

In operation of the system just described, the capacitor pickups may be applied as attachments to a conventional piano lyre. Operable distances and locations have already been referred to. It may be noted further that it is not essential that the capacitor pickups be located at any specific distances, taking into consideration opposite ends of the strings. A low power electric circuit is sufficient to properly operate the system. As the strings are struck with the usual conventional hammers, the strings vibrate. On those occasions where the sounding board has been removed, there will be almost no audible sound produced by the vibrating strings. Moreover, the character of the sound produced is of no consequence whatsoever, since there is no pickup of the audible sound. Furthermore, it is not of material consequence whether or not the sounding board be removed nor is it of consequence how true the sonic effect may be which is ordinarily produced by the instrument. So long as the strings are in tune and vibrate at the proper frequency, the frequency of vibration of the strings is the primary requisite and agency by means of which the sounds ultimately emanating from the loudspeaker system are created.

In the example shown, the capacitor circuit completed by the grounding of the strings of the piano is carried through the modulated oscillator 43. The loudness of the ultimately produced sound may be varied to an extent by adjustment of the pre-amplifier circuit. The vibrations translated into wave form in the electric circuit are in the embodiment chosen for the purpose of illustration frequency modulated and carried to the detector 44. It should be noted, however, that although the selected diagram suggests frequency modulation the system is also effective when other forms of modulation are employed as, for example, the customary amplitude modulation.

In the detector 44, unwanted frequencies may be bled ott and the desired frequencies passed to the pre-amplier 45. From here, the selected frequencies are set out through the lead 46 to any amplification and loudspeaker system of suitable rating to conform to the electrical characteristics of the system just described.

Although in the form of the device illustrated in Figure 1 the capacitor pickups are shown in a form adapted particularly as attachments to an already manufactured. piano, they can be altered in their physical form follow` ing the principles of the invention to be built into a piano at the outset. Furthermore, although the capacitor pickups are effective when applied to conventional Stringing as where strings at regular tone intervals are double strings or striple strings, different effects may be produced by an instrument wherein a single string produces the vibrations at each of the usual tone intervals. In order to provide an instrument capable of varying the effect of the capacitor output, means may be provided for damping out one or two of the strings where a triple formation of strings is employed at each tone interval, thereby leaving either a single remaining string or perhaps in some instances two strings instead of the initial three strings.

A mechanism for selectively damping out one or two strings of the usual three-string arrangement is illustrated in Figures 9 through 13, inclusive. As there shown, there is attached to the frame 11 a pair of oppositely disposed damping cam carriers and 61. The cam carriers are mounted upon brackets 62 and 63 fastened upon the frame 11 so that thecam carriers span all of the strings 30, for example, in a set of strings. The cam carriers are located immediately opposite each other, as indicated to good advantage in Figures ll, 12, and 13, so that they can press on opposite sides of the strings. The cam carriers are so built as to be provided with cam elements 63 and 64. The cam elements are fastened respectively to cam shafts 65 and 66 by keys 67 and 68. Between the cam elements, spacers 69 may be provided.

In Figure 12, the cam elements 63 and 64 are shown rotated to positions, wherein spiral cam surfaces 70 and 71 have been advanced into contact with one of the strings 30. Rotation of the cam shafts 65 and 66 by exactly equal increments is accomplished by employment of meshing gears 72 and 73 appropriately keyed to the respective cam shafts 65 and 66. A crank 74 may be shifted in a clockwise direction, as illustrated in Figure 13, to advance the cam faces to the locations indicated in Figure l2. In this adjustment, one of the strings of each set of three-is damped out. Thisleaves two strings of each set of three free to vibrate and produced aA desired tone quality sound. Should it be desired, however, to damp out two strings of each set of three, the cam carriers can be rotated still further in the direction indicated to bring cam elements 74 and 75 into contact with the string which lies between them. Cam elements 74 and 75, respectively, have cam surfaces 76 and 77 similar to the cam surfaces 70 and 71 but rotated a slight distance behind the cam surfaces 70 and y71 so that the largest portion of the cam surfaces are not brought against the strings simultaneously. By making small segments 78 and 79 of the cam faces 70 and 71 circular in perimeter, these faces will continue to bear against the appropriate string 30 with the same degree of pressure while the cam faces 76 and 77 are being advanced into contact with the string 30 lying between them. When, by manipulation of the crank 74', both pairs of cam elements have been rotated into contact with the outside strings of each trio of strings, only the central string will be permitted to vibrate when struck with the usual hammer. The capacitance effect produced by the single vibrating string carried through the electronic system will produce musical tones of somewhat different tone quality than when all three strings or even two strings are permitted to vibrate. The resultant effect will be one somewhat different from the normal enhanced tone quality of the conventional piano instrument.

There has accordingly been described herein an electronic stringed instrument which makes use of an oscillator modulated by a piano capacity reactor constructed as part of the string mechanism which is especially well adapted to the generation of extremely resonant, pleasing, and high quality music-al sounds reflecting the sound of very high grade pianos, where all the strings of the piano are employed even though the structure of the piano instrument may be otherwise of very general design and quality. The invention and system furthermore is one which is particularly versatile in character, in that it lends itself to modication by mechanical means in a fashion permitting variations in tone quality to be created and reproduced by a system which is extremely simple both mechanic-ally and electrically. The invention, moreover, is one of such simple and inexpensive character and construction as to make possible very high grade sounding piano instruments without resort to the familiar extremely high grade character of the instrument itself.

' While we have herein shown and described our invention in What We have conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of our invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of thc claims so as to embrace any and all equivalent devices.

The invention having herein been described, what is claimed as new and sought to be secured by Letters Patent is:

l. A tone reproduction system comprising a metallic frame, a set of stringsstrung on said frame and tuned to vibrate at diterent intervals when struck, said strings have a common electrical connection, an electric amplifying circuit comprising an electric capacitor element cooperable with the strings and forming with the strings a string capacitor, said capacitor element comprising an electric conductor havinga thickness of the same relativ., magnitude Aas the diameter of the strings and a breadth many times the thickness, damping means comprising sheets of relatively stili vibration damping and electric insulating material laminated to each other and to the electric conducting material on opposite sides thereof, and a plurality of mounts for said capacitor element comprising each vibration damping base of dielectric material on the frame, and an adjustable post on the basev and connected to said damping means, and resilient cushion means between said capacitor element and the frame whereby to enable positioning of the capacitor element at different distances from the strings in response to adjustment of said posts.

2. A tone reproduction system comprising a metallic frame, a set of strings strung on said frame and tuned to vibrate at diierent intervals when struck, said strings having a common electrical connection, an electric amplifying circuit comprising an electric capacitor element cooperable with the strings and forming with the strings a string capacitor, said capacitor element comprising an electric conductor having a thickness of the same `relative magnitude as the diameter ot the strings and abreadth many times the thickness, vdamping means comprisingY sheets of relatively sti vibration damping andelectric' insulating material laminated to each other and .to the electric .conducting material on opposite sides thereof, and a plurality of mounts for said capacitor element comprising each a vibration damping base of dielectric material on the frame, and a post on the base and con'- nected to said damping means, said posts numbering not less than three and being located on opposited sides of a longitudinal centerline.

3. A tone reproduction system comprising a metallic trame, a set of strings strung on said frame and tuned to vibrate at different intervals when struck, said strings having a common electrical connection, an electric am' plifying circuit comprising an electric capacitor element cooperable with the strings and forming with the strings a string capacitor, said capacitor element comprising an electric conductor having a thickness of the same relative magnitude as the diameter of the strings and a breadth many times the thickness, damping means comprising sheets of relatively stiff vibration damping and electric insulating material laminated to each other and to the electric conducting material on opposite sides thereof, and a plurality of mounts for said capacitor element comprising each a vibration damping base of dielectric material on the frame, and an adjustable post on the base and connected to said damping means, and resilient cushion means between said capacitor element and the frame whereby to enable positioning of the capacitor element at different distances from the strings in response to adjustment of said posts, said posts numbering not less than three and being located on opposite sides of a longitudinal center line.

References Cited in the file of this `patent UNITED STATES PATENTS v1,538,636 Westbrook `Juue 15, 1926 1,952,630 Palmgren 2 Mar. 27, 1934 2,032,435 Palmgren Mar. 3, 1936 2,200,718 Miessner May 14, 1940 2,220,350 Purington Nov. 5, 1940 2,473,442 Page June 14, l949 2,821,879 Sano Feb. 4, 1958 FOREIGN PATENTS 298,719 Great Britain oet. 1s, i928 

